[time-nuts] Linear voltage regulator hints...

[Bob Camp]

Hi


> On Dec 11, 2014, at 7:37 PM, xaos <xaos at darksmile.net> wrote:
> 
> I don't know if this is the right time to ask this but here goes.
> I have started a design for a linear power supply for the Beagleboard
> 
> 5V 5-10A. Over-Voltage, short circuit and temp protection.
> Very low ripple and HF noise.
> 
> I have been watching this thread and I am still not sure
> what device would give me what I want. I am not as good as
> some circuit designers here, to design a PS
> via discreet transistors. Dr. Bruce Griffiths comes to mind.
> He would probably do this with his eyes closed.
> 
> So, I need to use a regulator chip.

The simple answer is that a 78L05 style regulator will do just fine.

Bob

> 
> The TI TPS7A4700 looks great but it can only supply 1A.
> 
> Any other candidates ?
> 
> I am sorry if I am somehow asking an obvious question.
> 
> -George
> 
> On 12/11/2014 06:26 PM, Neil Schroeder wrote:
>> So I've done a lot of work in power lately and I can summarize some of this
>> quickly:
>> 
>> The lowest noise LDOs today are the TI TPSa4700/01 up to 36v/1a and about 4
>> uVRms noise,  and the ADP7154/55 up to 5.5v and 600ma with only *0.9* uVRms
>> above 100hz.
>> 
>> Both feature great PSRR -and in the case of the ADI part don't even
>> recommend filter caps at all.
>> 
>> The TI however does still recommend some capacitance.
>> 
>> Now most people's next question  is how to get their ruby or their
>> septuple-oven homebrew design powered by one. The quick answer is an error
>> amplifier based ldo balancer for the most accurate distribution of current.
>> Also helps with heat.
>> 
>> Will share a sketch when at my desk next.
>> 
>> 
>> On Thursday, December 11, 2014, Hal Murray <hmurray at megapathdsl.net> wrote:
>> 
>>> eb at telight.com <javascript:;> said:
>>>> If the plan is to use a three-terminal regulator after all, I'd  suggest
>>> not
>>>> using a low-dropout (LDO) type if the raw input supply is  noisy - the
>>> LDOs
>>>> usually have PNP output transistors (for positive  regulators), so may
>>> tend
>>>> to have poorer HF input ripple rejection  than equivalent ones with NPN
>>>> passers.
>>> In this context, what is "high"?
>>> 
>>> Why don't filter caps solve that end of the spectrum?
>>> 
>>> 
>>> --
>>> These are my opinions.  I hate spam.
>>> 
>>> 
>>> 
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